(1) Field of the Invention
The present invention relates to high-voltage circuit devices. More specifically, the present invention relates to a high-voltage hybrid circuit-breaker.
(2) Description of Related Art
The present invention relates to a high-voltage hybrid circuit-breaker.
Such a hybrid circuit-breaker comprises one interrupting chamber for each pole, which interrupting chamber uses a dielectric gas, e.g. sulfur hexafluoride (SF6) under pressure, and has its fixed contact connected to a first terminal of the network and connected in series with a switch that withstands the dU/dt of the re-establishment voltage transient, and that has its fixed contact connected to a second terminal of the network. The switch is often a so-called vacuum “bottle”.
Such a hybrid circuit-breaker having metal cladding and commonly referred to as being “metal-clad” is described in U.S. Pat. No. 4,458,119 in which the interrupting chamber and the bottle are connected in series and in alignment. In that circuit-breaker, the moving contacts of the chamber and of the bottle are connected to actuating means for moving them between respective open positions and respective closed positions by means of a single control. Those actuating means comprise a set of links for opening the contacts of the vacuum bottle before the contacts of the gas interrupting chamber are opened. Such a delay is, in general, about a few milliseconds (ms). It is caused by the stroke of the moving contact being shorter in the vacuum bottle than in the interrupting chamber.
That type of hybrid circuit-breaker raises the following technical problems.
Firstly, since the interrupting elements are in alignment, it is particularly voluminous.
In addition, its actuating means do not enable the delay to be adjusted easily. However, depending on the power of the hybrid circuit-breaker or depending on the dielectric gas used, it can be useful to adjust the length of a delay between opening of the interrupting chamber and opening of the bottle.
In order to solve those problems, it is possible to consider disposing the gas interrupting chamber and the vacuum bottle along two sloping axes, the moving contact of the interrupting chamber being extended by a longitudinal drive arrangement against which an element connected to the moving contact of the vacuum bottle is disposed in permanent contact, the single control urging the moving contact of the interrupting chamber to move in translation along the first axis, and the length and the shape of the drive arrangement guaranteeing that the moving contacts move in synchronized manner from their closed positions to their open positions and vice versa.
Such an arrangement for a hybrid circuit-breaker is described in patent Documents U.S. 2003/0089682 or WO 97/08723.
Unfortunately, such arrangements raise the following technical problems.
Once the moving contacts of the interrupting chamber and of the vacuum bottle are in their open positions, the interrupting chamber and the vacuum bottle remain in their open positions. However, in those open positions, all of the moving contacts and of the charged parts that are integral with or secured to them form an assembly that is at a “floating” potential, that behaves like a capacitor, and that can give rise to partial discharges that might degrade the circuit-breaker, e.g. in the live insulating parts, in particular when the voltage across the terminals of the circuit-breaker is high. That can lead to arcs re-striking, essentially due to the short distance between the contacts of the vacuum bottle.
That problem can generally be solved by installing disconnectors connected in series with the circuit-breaker.
However, if such additional installation is omitted, the performance of the circuit-breaker and its length of its life are adversely affected.